New U.S. daily high temperature records exceeded daily cold records in December by a ratio of 1.8 to 1, a margin of 80%. The overwhelming excess of heat records continued into New Year’s Day, when the 116 high maximum records set or tied absolutely crushed the one lonely low minimum record…. The annual value [of the high/low record ratio] was 2.8 to 1, well above the 2.3 to 1 in 2010. Data from NOAA.

Steve Scolnik at Capital Climate analyzed the data from NOAA’s National Climatic Data Center (NCDC) and created the chart above.

This graphic shows the ratio of record daily highs to record daily lows observed at about 1,800 weather stations in the 48 contiguous United States from January 1950 through September 2009. Each bar shows the proportion of record highs (red) to record lows (blue) for each decade. The 1960s and 1970s saw slightly more record daily lows than highs, but in the last 30 years record highs have increasingly predominated, with the ratio now about two-to-one for the 48 states as a whole.

So, yes, 2.8-to-1 (along with 2.3-to-1 for 2010) continues the warming trend of the past few decades.

Spurred by a warming climate, daily record high temperatures occurred twice as often as record lows over the last decade across the continental United States, new research shows. The ratio of record highs to lows is likely to increase dramatically in coming decades if emissions of greenhouse gases continue to climb.

“Climate change is making itself felt in terms of day-to-day weather in the United States,” says Gerald Meehl, the lead author and a senior scientist at the National Center for Atmospheric Research (NCAR). “The ways these records are being broken show how our climate is already shifting.”

The scientific paper itself is here (subs. req’d). And NCAR posted a video of lead author Meehl discussing his findings here. The study looked into the future and found that “if nations continue to increase their emissions of greenhouse gases in a ‘business as usual’ scenario, the U.S. ratio of daily record high to record low temperatures would increase to about 20-to-1 by mid-century and 50-to-1 by 2100.”

Here’s a Stanford release for Climatic Change study (PDF here) I wrote about in June:

Stanford climate scientists forecast permanently hotter summers

The tropics and much of the Northern Hemisphere are likely to experience an irreversible rise in summer temperatures within the next 20 to 60 years if atmospheric greenhouse gas concentrations continue to increase, according to a new climate study by Stanford University scientists….

“According to our projections, large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years,” said the study’s lead author, Noah Diffenbaugh, The study, based on observations and models, finds that most major countries, including the United States, are “likely to face unprecedented climate stresses even with the relatively moderate warming expected over the next half-century.”

Bottom line: By century’s end, extreme temperatures of up to 122°F would threaten most of the central, southern, and western U.S. Even worse, Houston and Washington, DC could experience temperatures exceeding 98°F for some 60 days a year.

The peak temperature analysis comes from a Geophysical Research Letters paper that focused on the annual-maximum “once-in-a-century” temperature. The key scientific point is that “the extremes rise faster than the means in a warming climate.”

The results, depicted above (in °C), are quite remarkable, especially when you consider that this is just the A1B scenario. In 2100, A1B hits about 700 ppm with average global temperatures “only” about 3°C (5 F) warmer than today.

On our current emissions path, these record temperatures could be seen closer to 2060 than 2100:

… values in excess of 50°C [122°F] in Australia, India, the Middle East, North Africa, the Sahel and equatorial and subtropical South America.

As you can see from the map, extreme temperature peaks are only slightly lower over large parts of this country. The study notes:

Such temperatures, if lasting for some days, are life threatening and receive relatively little attention in the climate change debate.

So now the question is, has anybody done an analysis of what global warming could do to intense heat waves that last very long times, weeks or months? The answer is yes, and the results of that study are more worrisome — and it also received relatively little attention.

The November 2005 study in the Proceedings of the National Academy of Sciences, “Fine-scale processes regulate the response of extreme events to global climate change,” found that “peak increases in extreme hot events are amplified by surface moisture feedbacks.” The study looked at the A2 scenario (about 850 ppm in 2100) in the second half of this century (from 2071 to 2095). It examined temperature rise projections, plus “fine-scale processes,” such as how local warming is affected by loss of snow cover and loss of soil moisture. I interviewed the lead author, Noah Diffenbaugh, of Purdue University, for my book.

Houston and Washington, DC would experience temperatures exceeding 98°F for some 60 days a year. Oklahoma would see temperatures above 110°F some 60 to 80 days a year. Much of Arizona would be subjected to temperatures of 105°F or more for 98 days out of the year–14 full weeks. We won’t call these heat waves anymore. As Diffenbaugh told me, “We will call them normal summers.”

And again, that’s not even the worst case, since it’s “only” based on 850 ppm.

The definitive NOAA-led U.S. climate impact report from 2010 warns of scorching 9 to 11°F warming over most of inland U.S. by 2090 with Kansas above 90°F some 120 days a year with 850 ppm. By 2090, it’ll be above 90°F some 120 days a year in Kansas — more than the entire summer. Much of Florida and Texas will exceed 90°F half the days of the year. These won’t be called heat waves anymore. Again, it’ll just be the “normal” climate.

And remember, high heat means dry areas become drier and humid areas become intolerable.

On our current emissions path, we may well exceed the A2 scenario and hit A1FI, 1000 ppm (see here). In a terrific March 2010 presentation, Climate scientist Katherine Hayhoe has a figure of what the A1FI would mean:

It’s actually far, far worse than indicated by the models because they do not take into account the fact that forests and indeed vegetation in general is dying off.

The background level of tropospheric ozone and concurrent nitrogen cascade are increasing just as is CO2, except ozone happens to be directly toxic to plants, which in addition to being damaged due to an impaired ability to photosynthesize, also become more susceptible to insects, disease, fungus, winterkill, windthrow and drought.

So if you factor in the impending loss of the major CO2 sink on earth, along with phytoplankton also in decline, I should think we are going to see vastly more heating than even these horrific models portend.

Is there solid evidence of shifts in humidity? Our past very hot, very dry summers seem to be being replaced by long stretches of hot and humid – feels like Torres Strait Islands before the monsoon breaks. Time to metamorphose into a possum and go nocturnal, ME